1. Field of the Invention
The invention generally relates to a broom machine especially adapted for construction and maintenance work on a railway roadbed or track, as for dressing the surface of the ballast bed between and along the sides of the rails, and for leveling and distributing ballast over the bed.
In particular, the invention is concerned with a sweeper bristle element employed in combination with a rotating drum and element support means for use on a railway roadbed or track cleaner.
2. Description of the Prior Art
Railway ballast comprises a thick layer of crushed limestone or similar material resting on a prepared base and in which the track cross ties are embedded and supported. The ballast bed is shaped to have a generally horizontal top face over the lengths of the ties, that is, between the rails and alongside the rails and to have sloped banks at and beyond the ends of the ties. Desirably, the top surface of the ballast is level with or slightly below the top faces of the ties, and the ties and rails should be free of loose ballast and debris.
Both in maintenance and in original construction of the roadbed, new ballast is dumped onto the roadbed from cars and is roughly distributed by a blade device, such as a plow or moldboard. It is not possible, however, for such a blade device to produce the desired finish condition in which the ballast is level with or slightly below the tops of the ties. A brush or broom implement can produce the desired distribution and surface condition. The sweeping of ballast, however, imposes a severe load on the broom so that brooms are subject to heavy wear and short life.
The prior art discloses brooms which are constructed with bristles comprised of lengths of steel cable removably fastened to the mandrel or drum of the broom and encased in sections of heavy-duty hose to control fraying of the cable. With such a broom, it was found that in ballast dressing operations, such steel cable bristles would last only about two hours and would sweep less than five miles of track before requiring replacement. Further, such bristles require significant replacement time and, generally, it took two men two full days to replace the bristles. With such steel-cable bristles, the broom gave less than one man-day of service for each four man-days of repair, and this was economically impractical.
To overcome this problem, bristle elements, as disclosed in U.S. Pat. No. 3,649,984 invented by Kershaw, et al., have been suggested. Therein is disclosed a bristle element which is replaceably mounted on a mandrel rotatable on a horizontal axis. The bristle elements have a core made of a bundle of parallel straight spring-steel splines or wires fixed together at one end in a detachable coupling and encased in a resilient sheath which binds the splines into mutually supporting relation and distributes flexing stress in them away from their fixed end. In effect, the bristles suggested by Kershaw, et al., are primarily steel bristles, attempting to use wire as the main item in the construction. It is very complex to manufacture and quite expensive to assemble because of the many and various components and the machining necessary to create the structure. Fundamentally, it provides the same function as a cable and differs only in that it includes straight instead of twisted wires. The straight wires still suffer from the eventual frazzle which occurs in a cable and the rubber casing only functions to hold the frazzled wires together for a slightly longer period of time before breakdown.